The shoulder joint is the most mobile and flexible joint in the human body. This joint controls the position of the upper arm and, due to the high flexibility of the joint, enables a tremendous range of motion. However, due largely to its high flexibility, the shoulder is frequently subject to injury leading to pain, inflammation and loss of motion. The humerus and the scapula are the two major components of the shoulder joint with a portion of the head of the humerus functioning substantially as a ball positioned in a rather shallow cup-like area of the scapula known as the glenoid fossa. Smooth articular cartilage covers both the head of the humerus and the glenoid fossa and, together with the action of synovial fluid, allows these surfaces to glide with little friction. The joint capsule comprised of strong ligaments connects the head of the humerus to the scapula at the glenoid fossa so as to both secure and help define the joint and resist dislocation.
Muscles attached to different parts of the shoulder are utilized to enable the upper arm to move. The deltoid is a large muscle attached medially to the scapula along the acromion and also attached to a portion of the clavicle. The lateral portion of the muscle crosses the shoulder joint and is attached to the humerus about halfway down its length. The deltoid is the strongest of the shoulder muscles. Its function is to raise the arm upward (or abduction).
Internally disposed in relation to the deltoid muscle, a group of muscles known as the “rotator cuff” helps stabilize the joint as well as enable further movements of the arm. More specifically, the rotator cuff is a group of four muscles forming a strong “cuff” about the joint formed by the head of the humerus and glenoid fossa. In addition to helping to stabilize this joint, these muscles provide rotation and stabilize position of the arm. The four muscles of the rotator cuff are the subscapularis; supraspinatus; infraspinatus and teres minor.
The subscapularis muscle is attached to the deep surface of the scapula and then passes in front of the humeral head. It inserts into the humerus at the lesser tuberosity. This muscle is used to internally rotate the shoulder (and arm) and to bring the arm down to the side of the body (a motion that is called “adduction”). Ordinarily, internal rotation of the shoulder, or abduction, results in rotation of the arm so that the palmar surface of the hand turns away from the body as the dorsum of the hand approaches the trunk. For example, internal rotation of the right shoulder ordinarily results in a counter-clockwise rotation of the right hand and internal rotation of the left shoulder results in a clock-wise rotation of the left hand.
The three remaining muscles of the rotator cuff each have medial insertions at posterior surface of the scapula and then extend posterior to the humeral head where each continue on to insert at the greater tuberosity of the humerus. Such insertions and path enable these muscles to externally rotate the shoulder (and, in regard to supraspinatus) abduct (or move the arm outward, away from the side of the body).
Each of the muscles of the rotator cuff are susceptible to injury such as sprains and muscle tears which can be debilitating. The supraspinatus muscle and tendon is especially susceptible to such injury and is the most commonly injured part of the rotator cuff due, in large part, to its position and path of contraction. However, any of these muscles and associated tendons can an are involved in rotator cuff injuries.
It is known that strengthening the rotator group of muscles through exercise can greatly reduce the chance of rotator cuff injury and/or re-injury. For this reason, it is also well known to perform internal and external rotations of the shoulder to keep these muscles in top condition. Such exercise is also utilized as part of rehabilitation programs for treatment of rotator cuff injuries. More specifically, such rehabilitation programs often progress from passive range of motion exercises to active-assisted range of motion exercise to strengthening exercises.
In the past, strengthening exercises for the rotator cuff muscles—including those used for rehabilitation and for prevention of injuries—included external rotation and internal rotation of the shoulder utilizing, for example, hand weights. Utilizing such weights, an individual might, for example lie on their side on the floor or a exercise bench with their upper arm parallel to their body and lower arm held 90 degrees in relation to the upper arm. Thereafter, the shoulder could be internally or externally rotated, while holding a weight, to perform resistive training.
Utilizing free weight exercise was of limited value in that, depending upon the user's position, it is difficult to obtain consistent resistance through, for example, a complete 180 degrees of internal or external rotation. A handheld weight, following an arch-like movement, will not provide consistent resistance. For example, when the user's shoulder is positioned so that the lower arm lies vertical (plumb), there is substantially no force exerted upon the rotator cuff muscles. However, as the shoulder rotates and the lower arm approaches a position parallel with the floor, the force provided by the weight acting upon the rotator cuff muscles will increase. Such exercises also require utilizing different barbells when greater or lesser resistance is required. Such techniques also make no allowance for control and achievement of a safe range of motion. Holding a free weight by hand, especially in regard to a rehabilitation exercise, may be dangerous in that the potential energy associated with the weight might cause a user to over-extend his or her movements—go beyond a range of motion in which such movement is safe—. Such free weight exercises make no provision for controlling range of motion (ROM). Also, if a user should suffer a spasm, sudden pain or lose consciousness, the potential energy stored in the free weight or the momentum developed could cause further injury to the user or others. In addition, performing both internal and external rotation of the shoulder with weights would most likely require a user to continually change position.
It has also been known, in the past, to utilize elastic bands and pulleys to exercise the muscles of the rotator cuff. More specifically, internal and external rotations of the shoulder have been accomplished utilizing an elastic band (or tube) fixed to a support, such as a door or pole. In such exercise, the individual may stand, sit or kneel, with her upper arm aligned with her torso and lower arm positioned at about 90 degrees in relation to the upper arm. Thereafter, the user grasps the free end of the tube or band and performs the desired rotation which is resisted by the elastic material. However, utilizing such an exercise device subjects a user to varying amounts of resistance as the band or tube is stretched and, similar to the use of weights, subjects the user to the danger of stored potential energy within the elastic posing a danger of injuring the user. Also, such elastics require the user to change position when he or she wishes to change from internal to external rotation exercises.
Pulley devices utilizing weights have also been known to be utilized for performing internal and external rotation shoulder exercises. However, as the case with hand weights and elastics, pulley machines also store potential energy during use which can result in the aforementioned injuries. Such machines also require a change in user position and/or machine configuration in order to perform both internal and external rotation exercises.
U.S. Pat. No. 4,878,663 discloses a rehabilitation and fitness apparatus which incorporates a range limiter disc. The disclosed device utilizes a rotating disc which is rotated through the action of an actuator bar. However, rather than using the range limiter disc to control the range of movement a user's shoulder could internally or externally rotate, the disclosed device uses the disc to set the actuator bar in a desired “start” position so as to enable one machine to be utilized to perform multiple exercises (such as internal and external shoulder rotation). The disclosed device utilizes a stack of weights to provide resistance to a user's motion which, of course, does entail the storing of potential energy and generation of momentum that can cause the aforementioned problems. The device does provide adjustment of resistance by the use of a pin to control the number of weights in the stack utilized.
U.S. Pat. No. 4,957,281 discloses a rotator cuff therapeutic exercise device which includes a stack of weights supported by a frame which are raised in a working stroke from a rest position, against gravitational force, to a raised position (with stored potential energy). An actuator mechanism on the frame is specifically shaped and configured to be gripped and rotated by the hand of a user to move the weights along the working stroke. The actuator mechanism may be adjusted to a first or second position for enabling a corresponding rotational working motion of the one of the user's arms whose hand grips the actuator mechanism. This device, as discussed above in regard to free weight exercise and elastic resistance machines, stores potential energy and develops considerable momentum which may be damaging to a user and includes no means of controlling the range of motion during inward or outward rotation. The machine also requires manual adjustment to change resistance.
U.S. Pat. No. 5,080,350 discloses a rehabilitation/exercise device wherein elevational adjustment is provided. However, the device disclosed in this patent provides no means to provide limitation to internal or external rotation of a shoulder. The subject device utilizes a brake and brake drum to provide resistance.
Ideally, a shoulder rehabilitation/exercise device should: a. enable an individual to perform internal and external rotations of the shoulder wherein the device: b. enable performance of inward and outward rotations of both the right and left shoulders without having to adjust the device or re-position the user; c. provide secure, stable, and adjustable positioning of a user's elbow; d. provide adjustment to accommodate arm's of varying length; e. provide adjustment of the angle formed between the upper and lower arm; f. provides a means of controlling the range of motion a user may operate the device during such operation; g. provide fluid-like resistance during exercise so as to prevent injury to the shoulder joint; h. exerts no substantial force which would otherwise continue movement of the device after a user has terminated operation thereof; i. enable adjustment of device resistance without having to manually adjust the device; and j. enable manual adjustment in regard to device resistance when such is advantageous.